1. Field of the Invention
The present invention relates to a driver for driving a semiconductor optical modulator.
2. Related Background Art
A traveling wave amplifier (hereafter denoted as “TWA”) has been well known in the field. A TWA generally provides a plurality of cells each connected in parallel between the input interconnection and the output interconnection and amplifying an input signal coming therein with an input delay time specific to the cell and output an amplified signal to the output terminal with an output delay time also specific to the cell. But the sum of the input delay time and the output delay time is common to respective cells; accordingly, the output signal may be kept in the waveform thereof. The cells are powered through the output interconnection.
When an TWA is utilized in an optical communication, in particular, when an TWA drives an optical modulator types of an electro-absorption (hereafter denoted as “EA”) modulator or a Mach-Zehnder (hereafter denoted as “MZ”) modulator, a substantial amplitude of the output signal is required, which increases a driving current flowing in the driver. A TWA generally requires delay lines. When the driving current with the substantial amplitude flows in the delay lines, the delay lines are inevitable to be widened in dimensions thereof, which enlarges a size of the TWA.